Spacecraft formation flying in the port-Hamiltonian framework

The problem of controlling the relative position and velocity in multi-spacecraft formation flying in the planetary orbits is an enabling technology for current and future research. This paper proposes a family of tracking controllers for different dynamics of Spacecraft Formation Flying (SFF) in the framework of port-Hamiltonian (pH) systems through application of timed Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC). The leader–multi-follower architecture is used to address this problem. In this regard, first we model the spacecraft motion in the pH framework in the Earth Centered Inertial frame and then transform it to the Hill frame which is a special local coordinate system. By this technique, we may present a unified structure which encompasses linear/nonlinear dynamics, with/without perturbation. Then, using the timed IDA-PBC method and the contraction analysis, a new method for controlling a family of SFF dynamics is developed. The numerical simulations show the efficiency of the approach in two different cases of missions.

     

An investigation on the influence of the shape of the vortex generator on fluid flow and turbulent heat transfer of hybrid nanofluid in a channel

Journal of Thermal Analysis and Calorimetry - The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a...     

Kinetic determination of silver ion by its perturbation on Belousov-Zhabotinskii oscillating chemical reaction using potentiometric method.

Silver ion can perturb the Belousov-Zhabotinskii (B-Z) oscillating chemical reaction. Therefore, the B-Z oscillating system was applied in the determination of silver ion by using a platinum wire as an indicator electrode in the potentiometric method. The amplitude of the potentiometric oscillation increased linearly in proportion to [Ag+] in the range of 9.42 x 10(-6) M to 2.54 x 10(-4) M, with a correlation coefficient of 0.999 under the optimum conditions. The obtained LOD (2sigma) was 8.85 x 10(-6) M and the relative standard deviation (RSD) for five measurements of 1 x 10(-4) M silver ion was 5%. The influence of some potentially interference was also investigated.     

Spectrophotometric study of the complexation of iodine with 1,7-diaza-15-crown-5 in chloroform solution

The complex formation reaction between iodine and 1,7-diaza-15-crown-5 (DA15C5) has been studied spectrophotometrically in chloroform at 25°C. The resulting 1:2 (DA15C5:I₂) molecular complex was formulated as (DA15C5...;I⁺)I ₃ ^– . The spectrophotometric results, as well as the conductivity measurements, revealed that the gradual release of triiodide ion from its contact ion paired form in the molecular complex into the solution is the rate determining step of the reaction. The rate constant was calculated ask=(8.8±0.2)×10^–3 min^–1. The formation constant of the molecular complex was evaluated from the computer fitting of the absorbance-mole ratio data as logK _f=6.89±0.09.     

Old Reagent,New Results: Aromatization of Hantzsch 1,4-Dihydropyridines with Supported Bismuth Nitrate under Microwave Irradiation in Solventless System

Hantzsch 1,4-dihydropyriines were rapidly and efficiently oxidized using bismuth nitrate supported onto silica gel under microwave irradiation.     

Effect of Al2O3 nanoparticles on the steel-glass/epoxy composite joint bonded by a two-component structural acrylic adhesive

This paper reports a study on the effect of Al₂O₃ nanoparticles on the adhesion strength of steel-glass/epoxy composite joints bonded by a two-component structural acrylic adhesive. The addition of Al₂O₃ nanoparticles to the two-component acrylic adhesive led to a remarkable enhancement in the shear and tensile strength of the composite joints. The shear and tensile strength of the adhesive joints increased by addition of Al₂O₃ up to 1.5 wt%, which decreased by further addition of the nanofiller. Introduction of the nanoparticles caused a reduction in the peel strength of the joints. DSC analysis revealed that the glass transition temperature (Tg) of the adhesives rose by increasing the nanofiller content. The advancing water contact angle was decreased for adhesives containing nanoparticles. SEM micrographs indicated good dispersions of the Al₂O₃ nanoparticles within the acrylic matrix in the specimens with up to 1.5 wt% Al₂O₃ and revealed that addition of nanoparticles altered the fracture morphology from smooth to rough fracture surfaces.     

An active and selective heterogeneous catalytic system for Michael addition

Potassium fluoride doped natural zeolite was found to be an efficient and selective solid base catalyst for 1,4-Michael addition. The catalyst is easily prepared and the workup procedure simplified by simple filtration.All products were obtained in high yields as well as short reaction times.     

Copper-based metal–organic framework decorated by CuO hair-like nanostructures: Electrocatalyst for oxygen evolution reaction

We report a Cu-based metal–organic framework (MOF) decorated by CuO nanostructures as an efficient catalyst for the oxygen evolution reaction (OER). MIL-53(Cu) was synthesized by a hydrothermal approach using 1,4-bezenedicarboxylic acid as organic precursor and further annealed at 300°C to form CuO nanostructures on its surface. The produced electrocatalyst, CuO@MIL-53(Cu), was characterized using various techniques. Under alkaline conditions, the developed electrocatalyst exhibited an overpotential of 801 and 336 mV versus RHE at 10 and 1 mA cm⁻², respectively. The reproducibility of the catalytic performance was validated using several electrodes. It was confirmed that the CuO hair-like nanostructures grown on MIL-53(Cu) using thermal treatment exhibit high OER activity, good kinetics and durability. CuO@MIL-53(Cu) is an economic noble-metal-free OER electrocatalyst. It has potential for application as anode material for sustainable energy technologies like batteries, fuel cells and water electrolysis.     

Application of chromium‐doped fullerene as a carrier for thymine and uracil nucleotides: Comprehensive density functional theory calculations

The interactions of the nucleobases thymine (C₅H₆N₂O₂) and uracil (C₄H₄N₂O₂) with Cr‐doped C₂₀ fullerene (C₁₉Cr) are investigated by performing density functional theory calculations. The adsorption of these nucleobases on C₁₉Cr leads to two distinct geometries (P1 and P2) differing in the orientation of the nucleobases. The interaction of the nucleobases with the C₁₉Cr nanocluster is highly exothermic, revealing that they are chemically adsorbed on C₁₉Cr. The results show that the binding energy of the thymine–C₁₉Cr complex is slightly higher than that of the uracil–C₁₉Cr complex. In addition, the P2 geometry is more stable compared to P1 due to the higher binding energy in the former configuration. However, based on the results of natural bond orbital and frontier molecular orbitals analyses, the C₁₉Cr nanocage has higher reactivity with the nucleobases in P1 geometry in comparison with P2 due to the larger charge transfer and orbital hybridization in the former geometry. Moreover, the band gap of the C₁₉Cr nanocage decreases after interaction with the nucleobases, and interestingly the impact is more pronounced for P1 geometry, confirming the higher sensitivity of C₁₉Cr to the nucleobases in P1 geometry. Our findings reveal the promising potential of C₁₉Cr as an organometallic carrier for nucleobases thymine and uracil.